Piston



F. J. MCALLISTER PISTON Filed Jan. 12, 1942 INVENTOR.

FRAIVK JIMCALLISTER 1 W W Patented Oct. 17, 1944 UNITED STATES I PATENT OFFICE 2,360,568 PISTON Frank J. McAllister, Denver, 0010. Application January 12, 1942, Serial No. 426,489

12 Claims.

This invention relates to improvements in-pistons or piston assemblies for internal combustion engines and the like.

As is well known to persons skilled in this art, the interior walls of cylinders of internal combustion engines tend to Wear oversize, which causes a loose fit of the piston in the cylinder resulting in general inefiiciency. Furthermore, such cylinders are inclined to wear out of round, which further detracts from efiicient operation of the engine.

A. general object of the present invention is to provide a piston for an internal combustion englue or the like, which will overcome the faults hereinabove enumerated and tend materially to increase the eificiency and the life of such engines.

More particularly, a principal object of the present invention is to provide a two-part piston for internal combustion engines or the like, which has means for effective radial expansion to take up and compensate for wear that may occur between the piston and the interior walls rof its cooperating cylinder.

Another object is to provide such a piston that has means that tend to prevent the wearing of a cylinder out of round.

A further object is to provide a piston that has means for selective longitudinal positioning in the cylinder with reference to the head of the cylinder and with reference to the connecting rod with which such pistons are always associated.

Other objects and advantages will become manifest as this disclosure proceeds.

In order to disclose an operative reduction to practice of the present inventiveconcept, the accompanying drawing, which is made a part hereof, will be described in some particularity.

In the drawing,

Figure l is a general elevation of a piston made according to the present invention;

Figure 2 is a bottom view thereof looking up into the piston; and

Figure '3 is a vertical longitudinal section taken approximately along the center line of a piston that is similar to the one illustrated in Figures 1 and 2.

Reference character 5 denotes the upper or head section of a piston, while the lower or skirt section is indicated at 6. An annular shim l is positioned between. the two sections which are securely fastened together as by bolts 8 which are placed through two sets of radial arms 9 which; are correspondinglyv and adj acently positioned on the respective sections 5 and 6 of the piston. 1

A resilient helical metallic coil of rectangular cross section is indicated by reference character I0 and is placed around the exterior of the piston assembly in a; groove of corresponding size and shape. This coil It provides a resilient seal between the piston and the walls of the cylinder and performs the function of the ordinary piston rings. The exact shape, size and number of turns of 'the coil ID are, of course, subject to optional variation according to preferred practice in any given installation.

In the upper or head section 5 of the piston is located a central boss I 2 that is internally threaded as indicated-at l3. This boss preferably connects the head of the piston with the upper set of radial arms 9.

Another central boss I4 is carried on th lower set of radial arms 9 that are an integral part of the lower section 6 of the piston. V

A central threaded stud l5 extends upwardly through the boss M which acts as a guideway therefor, and is threadedly engaged in the upper boss l2. Set screws l6 hold the stud 15 in selected positions with reference to the head section 5 of the piston.

On the lower end of the stud I5 is a ball I! which is an integral part of said stud and which preferably is made of a high grade steel alloy of great tensile strength.

A connecting rod l 8 is provided at its upper end with a socket l9, one-half 26 of which is preferably an integral part of the connecting rod l8, while the other half 2| of the socket is a separable piece terminating at its lower end in a wedge-like angle or V 22, and which is secured to the connecting rod by means of a plurality of bolts 23. In its assembled operating position, the socket l9 embraces the ball I! to provide a universal joint between the piston and the connecting rod.

In use, the piston is initially assembled as illus- I trated and described, the piston being positioned in the cylinder with reference to the head thereof and with reference to the connecting rod as desired.

.Since the connection between the piston and the connecting rod is a ball and socket joint providing. universal relative movement of the piston with reference to the connecting rod, there will be little or-no tendency for thepiston to wear the cylinder out of round as ordinarily happens with the conventional wrist-pin connection of a piston with a connecting rod.

The wrist-pin connection as ordinarily used provides only for swinging movement of the connecting rod with reference to the piston in one plane. The present construction provides for relative movement between the piston and the connecting rod in any direction, thus permitting the piston to follow and be guided by the cylinder walls in the line of least resistance. The helical coil It) also tends to cause the piston to turn slightly in the cylinder, thereby cooperating with the ball and socket joint in preventing the piston from wearing the cylinder out of round. Such turning will tend to take place more often on the suction stroke. In the case of a four-cycle internal combustion engine, the piston is freer at that time than on either the explosion, compression, or exhaust strokes, as the pressure is greater on these strokes thanon the suction stroke. In the case of an air compressor or the like, there are only suction and compression strokes and the pressure against the piston is less on the suction stroke. Thus, the piston will turn or rotate in the cylinder, normally at a very slow rate.

When normal wear causes the cylinder to become oversize, then the piston may be partially disassembled and the shim I removed, after which the piston is reassembled. In reassembling the piston after removal of the shim 1, the over-all length of the pistonis shortened thus tending to increase the diameter of the coil Ill so that it will fit the enlarged bore of the cylinder. This is an extremely simple and efficient way to compensate for the wear of the cylinder walls and eliminates the necessity of reboring the cylinders and fitting them with oversize pistons as has been common practice heretofore.

Since the coil it! extends eifectively from one end of the piston to the other, there is no piston slap as may frequently occur Where the ordinary rings are used and the cylinder becomes enlarged by wear.

The threaded connection of the stud l5 with the boss l2 provides for further compensating adjustment of the piston head with reference to the connecting rod when the piston is'thus taken apart and reassembled, or at any other time such an adjustment may be desired.

It is now manifest that the present piston will improve the efficiency and prolong the life of internal combustion motors or the like, and that it tends to overcome some of the principal difiiculties heretofore encountered in the use and maintenance of such engines.

By the use of pistons made according to this invention, much time and expense may be saved in servicing, repairing and reconditioning engines provided therewith.

The present piston may also be used for other purposes such as pumps, compressors or the like, and it is not limited to any particular kind of use. The materials, sizes and proportions of this piston will be determined by the circumstances at the time of its manufacture and the purpose for which it is intended.

Obviously, when the shim I is removed and the two sections 5 and 6 of the piston are brought closer together, the continuity of the helical groove in which the coil I0 is placed, will be slightly disrupted. This factor can be taken care of by providing a groove that is somewhat oversize as to its width, adjacent the predetermined line of separation and union of the sec-.

tions.

The generic structural features herein set forth are adaptable to a wide field of practical utility. The present drawing merely illustrates a typical example and should not be construed to express or to imply any limitation to this invention, the scope of which is, in reality, measured by the appended claims.

What I claim and desire to secure by Letters Patent is:

1. A piston of the character described comprising an upper head section, a separable lower skirt section, a resilient helical coil positioned around the exterior of said sections, there being a corresponding groove for the reception of said coil, means for adjusting the diameter of the helical coil consisting of a shim normally positioned between and separating the sections, and means for separably fastening the sections together.

2. In a'piston of the character described, a head section, a separable skirt section mounted on the head section for limited lengthwise movement relative thereto, each section having a hellcal groove along its periphery constructed and arranged to join as a unit, a resilient spiral pack ing fitted in said grooves throughout substan' tially the combined range thereof, and means for varying the lengthwise relation of said sections to change the effective diameter of the piston.

3. In a piston of the character described, a head section, a separable skirt section mounted on the head section for limited lengthwise movement relative thereto, each section having a helical groove along its periphery constructed and, arranged to join as a unit, a resilient spiral packing fitted in said grooves throughout substantially the combined range thereof, means for adjusting the diameter of the helical coil con-' sisting of a shim normally positioned between and separating said head and skirt sections, and means for separably fastening the sections together.

4. In a piston of the character described, a

' head section, a separable skirt section supported from the head section in spaced relation thereto for limited lengthwise movement, each section having a helical groove along its periphery constructed and arranged to join as a unit, a resilient spiral packing fitted in said grooves throughout substantially the combined range thereof, and means for moving said sections into closer proximity to thereby change the efiective diameter of the piston.

5. In a piston of the character described, a head section, a separable skirt section mounted on'the head section for limited lengthwise movement relative thereto, each section having a helical groove along its periphery constructed and arranged to join as a unit, a resilient spiral packing of rectangular section fitted in said grooves throughout substantially the combined range thereof, and means for varying the length-- Wise relation of said sections to change the effective diameter of the piston.

6. In a piston of the character described, a head section, a separable skirt section mounted on the head section for limited lengthwise movement relative thereto, each section having a helical groove along its periphery constructed and arranged to join as a unit, a resilient spiral packing fitted in said grooves throughout substantially the combined range thereof, said grooves being widened adjacent the joint of the sections to accommodate changed positions of the spiral packing, and means for varying the lengthwise relation of said sections to change the efiective diameter of the piston.

7. A piston comprising separable head and skirt sections, each said section having a helical groove along its periphery constructed and arranged to join as a unit, a spiral packing fitted in said grooves throughout substantially the combined range thereof, means for adjusting the diameter of the helical coil consisting of a shim normally positioned between and separating said head and skirt sections, means for separably fastening the sections together, and means for attachment of said piston on a connecting rod, comprising a threaded socket member on the interior of the head section, and a guideway on the skirt member disposed in axial alinement with said socket member.

8. A piston comprising separable head and skirt sections, each said section having a helical groove along its periphery constructed and arranged to join as a unit, a spiral packing fitted in said grooves throughout substantially the combined range thereof, means for adjusting the diameter of the helical coil consisting of a shim normally positioned between and separating said head and skirt sections, means for separably fastening the sections together, and means for attachment of said piston on a connecting rod, comprising a threaded socket member on the interior of the head section, a guidewayon the skirt member disposed in axial alinement with said socket member, and means on said skirt section adapted to clampingly engage a connecting rod extended through said guideway into said socket member.

9. A piston comprising separable head and skirt sections, each said section having a helical groove along its periphery constructed and arranged to join as a unit, a spiral packing fitted in said grooves throughout substantially the combined range thereof, means for adjusting the diameter of the helical coil consisting of a shim normally positioned between and separating said head and skirt sections, means for separably fastening the sections together, and means for attachment of said piston on a connecting rod, comprising a threaded socket member on the interior of the head section, a guideway on the skirt member disposed in axial alinement with said socket member, and means including opposed set screws on said skirt section adapted to clampingly engage a connecting rod extended through said guideway into said socket member.

10. An assembly of the character described comprising, in combination, a piston having a helical groove about its periphery, a resilient spiral packing fitted in said groove, a connecting rod, and a universal joint connecting said rod and said piston.

11. An assembly as defined in claim 10, wherein said universal joint comprises a ball and socket joint.

12. An assembly as defined in claim 10, wherein said piston is adjustable longitudinally with respect to said universal joint.

FRANK J. MCALLIS'IER. 

